Turbine blade

Abstract

The invention is intended to reduce the profile loss. For that purpose, according to the invention, a plurality of turbine blades are arranged in the circumferential direction of a turbine driven by a working fluid. Each of the turbine blade is formed such that the curvature of a blade suction surface, which is defined by the reciprocal of the radius of curvature of a blade surface on the blade suction surface side, is decreased monotonously from a blade leading edge defined as the upstream-most point of the blade in the axial direction toward a blade trailing edge defined as the downstream-most point of the blade in the axial direction.

1 . A turbine blade which is arranged in plural in the circumferential direction of a turbine driven by a working fluid, 
 wherein said turbine blade is formed such that the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the reciprocal of the radius of curvature of a blade surface on the blade suction surface side by a pitch defined by the distance between two adjacent blades in the circumferential direction, is set to a constant value in a region from a blade leading edge defined as the upstream-riost point of the blade in the axial direction toward a point most projecting on the blade suction surface side and is decreased monotonously from said point most projecting on the blade suction surface side toward a point where the distance to a pressure surface of another adjacent blade is minimized.    
   
   
       2 . A turbine blade according to  claim 1 , wherein, assuming that a point at which a vertical line drawn from the blade trailing edge toward a tangential line with respect to the blade suction surface at the blade trailing edge crosses a blade pressure surface is defined as a trailing edge of the blade pressure surface, an angle at which the tangential line with respect to the blade suction surface at the blade trailing edge and a tangential line with respect to the blade pressure surface at the blade pressure-surface trailing edge cross each other is set to be not larger than 6 degrees.  
   
   
       3 . A turbine blade according to  claim 1 , wherein the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the curvature of the blade suction surface at the trailing leading edge by a pitch defined by the distance between two adjacent blades in the circumferential direction, is set to a certain value between 6 and 9.  
   
   
       4 . A turbine blade according to  claim 1 , wherein the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the curvature of the blade suction surface at a throat position, defined as a position where an inter-blade flow passage is narrowest, by a pitch, is set to a value between 0.5 and 1.5.  
   
   
       5 . A turbine comprising a plurality of stator blades and moving blades arranged in the circumferential direction of a rotor, a row of said stator blades and a row of said moving blades constituting a turbine stage, 
 wherein said stator blades are each formed such that the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the reciprocal of the radius of curvature of a blade surface on the blade suction surface side by a pitch defined by the distance between two adjacent blades in the circumferential direction is set to a constant value from a blade leading edge defined as the upstream-most point of the blade in the axial direction toward a point most projecting on the blade in the axial direction toward a point most projection on the blade suction surface side, and is decreased monotonously from said point most projecting on the blade suction surface side toward a point where the distance to a pressure surface of another adjacent blade is minimized.